Seth Rogen’s being a grown-up again. Fear not, those who remember Ro-Bro’s crying scene in Take This Waltz – this time the relationship stuff is played way down in the dirt. Bad Neighbours – writer-director Nicholas Stoller’s smart, disgusting gutter-dweller – has little time for the intricacies of long-term love and commitment. Instead it crashes Project X into a Joe Swanberg movie, invites it to chug the drinks and throw up all over the rug.

Rogen and Rose Byrne star as Mac and Kelly, new parents who go to war against the college fraternity that have moved in next door. Head of the frat pack is Zac Efron as Teddy, a sweet-natured lunk who doesn’t want to keep the couple’s baby awake, but can’t pass up an opportunity to party.

Stoller – the long-term Apatow collaborator who also had a hand in 2011’s Muppets revamp – has always been good at mixing profanity and pathos. His directorial debut, Forgetting Sarah Marshall, hid a sincere romantic drama behind all the dick jokes. Neighbors is far less subtle, barely bothering to check if its dignity’s in place before leaping into the next filthy setup.

Rogen and Byrne have great chemistry as the thirtysomethings anxious to do right by their daughter, look cool in front of the kids and still get invited to party like they used to. Byrne’s role is meatier than most comedies – even Apatow comedies – allow their female stars. Kelly is as conniving as Mac, equally keen to get one over the college kids by doing something moronic. They’re a very likable couple, both as tempted by the hard partying lifestyle of Teddy and co as they are dismissive of it.

Efron is strangely blank for the alpha-male leader of a group of marauding teens, but his support – including Dave Franco as his big-brained lieutenant, Pete, and Christopher Mintz-Plasse as “blessed” numbskull Scoonie – pick up the slack. Submarine’s Craig Roberts pops up in a charming little role as a wannabe frat member. He’s full of conflicted emotions about his place in the all-male society, unsure how the house’s intensely homo-social heirarchy chimes with his need for independence. His character is called Assjuice.

Bad Neighbours needs a tuck. The pacing is wobbly, the targets are too big. There are some lazy gags about post-natal sex (“she’s got these huge tits, but she insists on wearing a wife-beater. It’s like fucking Tony Soprano!”) and too much focus on Scoonie’s schlong. But it’s also an extremely funny comedy that pushes Rogen’s instinctive good nature to the limit. His stoner schtick helps to take the edge off much of the film’s crassness and gives it back some charm.

• This review was first published to coincide with the SXSW premiere of Bad Neighbours